Torsional vibration damper

ABSTRACT

A torsional vibration damper having a stator and a rotor provided with stator vanes and rotor wanes, respectively, which are arranged so as to form a plurality of work chambers fillable with damping medium and alternately changing their volumes during oscillation of the rotor. A damping device is provided in the rotor and has a compensation space in flow communication with the work chambers. The damping device has a throttle point configured so as to allow the compensation space to be pressurized by a relatively low pressure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention pertains to a torsional vibration damper, especially for a motor vehicle body.

2. Description of the Related Art

U.S. Pat. No. 6,082,507, which represents the basic type of device in question, describes a torsional vibration damper comprising:

-   -   a vane-equipped stator and a vaned rotor, where the stator and         the rotor form at least two working chambers filled with damping         medium, which chambers change their volume in opposite         directions during the oscillating movement; and     -   at least one damping device, which is connected to at least one         of the working chambers, where the working chamber connected to         the damping device has at least one flow connection leading to         the damping device, where the damping device has a collecting         space, which is connected via the flow connections to each of         the working chambers, the collecting space being divided in two,         where each of the collecting spaces connects all of the working         chambers of one rotational direction, the two individual         collecting spaces being separated by a partition, in which the         damping device is installed, where at least one of the         collecting spaces is in working connection with a         pre-pressurized compensating space.

In this type of vibration damper, the compensating space must be pre-pressurized in such a way that, for one rotational direction of the rotor, the maximum achievable damping pressure is lower than the pre-pressurization, because otherwise the separating piston would be pushed against the gas cushion in the compensating space. For this reason, a comparatively high level of pre-pressurization in the compensating space is chosen. This results in a high overall pressure level within the torsional vibration damper, as a result of which increased frictional forces occur between the rotor and the stator. It is already pointed out in U.S. Pat. No. 6,082,507 that the collecting space at the lower pressure level should be in working connection with the compensating space; nevertheless, the task still remains of lowering the level of the pre-pressurization in the compensating space below that present according to the state of the art.

SUMMARY OF THE INVENTION

This task is accomplished in accordance with the invention in that a throttle point is provided between the damping device and the compensating space.

The throttle point produces a pressure gradient between the collecting space and the compensating space, so that the pre-pressurization in the compensating space can be made lower than that according to the state of the art.

The throttle point can be designed in a variety of ways. The compensating space serves primarily to compensate for temperature-caused changes in the volume of the damping medium within the torsional vibration damper. The volumes which are present, and especially the flow velocities which are present, are comparatively low. For this reason, the throttle point tends to exert a stronger throttling effect at higher flow velocities. The flow velocities which occur during the operation of the damper are much higher than the volume flow rates caused by temperature. If the throttle point is provided with an appropriately small cross section, a backpressure will build up, so that practically no damping medium will pass over from the damping device to the compensating space.

In a further advantageous embodiment, the throttle point acts in a directionally dependent manner. During the operation of the damper, the damping medium heats up. When installed in a chassis, the torsional vibration damper is cooled by the wind created by the motion of the vehicle. Very strong and especially very fast cooling effects can occur in rainy or snowy weather. The cooling effect can therefore occur more rapidly than the heating effect produced by the operation of the damper. It is for this reason that the throttle point acts in a directionally dependent manner.

It is advantageous for a check valve, which is closed when the flow is arriving from the collecting space, to be connected in parallel with the throttle point.

According to an especially simple embodiment, the throttle point is formed by a porous component. A porous component consisting of sintered material has been found to be a very simple and low-cost solution. Alternatively, a throttle point can also be designed in the form of a channel cooperating with a cover disk, so that the size of the throttle cross section between the cover disk and the channel can be controlled very precisely.

As a further elaboration, the compensating space is located on the same center axis as the collecting space, and a second partition containing the throttle point extends between the compensating space and the damping device.

The damping device and the second partition are designed as ring-shaped pistons and together with a support rod form a single structural unit. This unit can be prefabricated independently of the overall torsional vibration damper. It is also possible for the ring-shaped piston for the damping device to be identical, as a component, to the second partition. The two components can be made to serve their different functions by providing the flow channels inside the ring-shaped pistons with the desired components.

The invention will be explained in greater detail below on the basis of the following description of the figures:

Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a longitudinal section through a torsional vibration damper; and

FIG. 2 shows a cross section of a torsional vibration damper.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Both FIGS. 1 and 2 illustrate the design of a torsional vibration damper 1. A rotor 3, which is supported so that it can oscillate with respect to a stator 5, has a tubular base body 7, which carries vanes 9, extending in the axial direction. The stator 5 carries ribs 13 on the inside wall of a cylinder 11, these ribs being parallel to the vanes. The base body 7 with its vanes 9, the cylinder 11 with its ribs 13, and the covers 15, 17 at the two ends of the stator form the working chambers 19, 21, where the working chambers with the same reference numbers change their volume synchronously during the oscillating movement of the rotor. The covers 15, 17 and the cylinder 11 can be joined to form a housing by simply flanging over the edges of the cylinder. Adjacent working chambers 19, 21 are separated hydraulically from each other by seals 23, 25.

Working chambers with the same reference numbers are connected in each case via radial channels 27 a, b, c and 29 a, b, c to collecting spaces 31, 33, respectively. A first stationary partition 35 is installed inside the tubular base body 7, between the two collecting spaces 31, 33. This partition is designed as a damping device with damping valves 37, 39, one for each of the two different directions of flow. The volume within the working chambers is pumped back and forth via the damping device. To compensate for temperature-caused changes in volume, a compensating space 41 is provided on the same center axis as the collecting space and in series with it, inside the tubular base body. The compensating space is completely filled with a damping medium and is separated by an axially movable separating piston 43 from a pre-pressurized gas space 45. The other end of the gas space is closed off by a cover 71. The gas space can be filled very easily through the open end of the tubular base body.

A throttle point 47 is provided between the damping valve 37 and the compensating space 41. FIG. 1 shows two design variants. First, as shown in the upper half of the figure, a porous component 49 made of sintered material, for example, can be used. It is important for the throttle point to exert a strong damping force at high flow velocities. Alternatively, it is also possible to use a second partition 51, in which a throttle point 47 is installed. A channel 53, which is at least partially covered by a disk 55, will be provided in this case. The throttle point could also be realized by stamping the side facing the disk 55 or by making a cutout in the disk.

It is also possible to connect a check valve 57 functionally in parallel with the throttle point 47, so that the throttle point acts in a directionally dependent manner.

The two partitions 35, 51 are designed as ring-shaped pistons, which, together with a support rod 59, form a prefabricatable unit. The support rod in turn is permanently connected to a second cover 61 on the rotor. The torsional vibration damper can be filled with a damping medium very easily through this cover.

When the rotor 3 pivots in the counterclockwise direction, the volume of the working chambers 19 decreases. The damping medium thus displaced is forced through the radial channels 29 a, b, c into the collecting space 31 and arrives at the damping valve 37 of the damping device 35. The damping valve 37 opens to a greater or lesser extent as a function of the pressure level, thus allowing damping medium to flow from the collecting space 33 into the working chambers 21, the volumes of which are increasing at the same time. The pressure of the damping medium in the collecting space 33 is also acting on the second partition 51 or on the porous component 49. The throttle point 47, however, allows only a very small volume flow rate to pass through, so that there's a significant pressure gradient with respect to the compensating space 41, this gradient being determined in turn by the pre-pressurization of the gas space 45.

When the rotor pivots in the clockwise direction, the collecting space 33 containing damping medium is put under pressure. The second partition with the throttle point 47 acts to absorb the pressure acting on the damping valve 39. As a result, the damping force which can be reached at the damping valve 39 no longer depends just on the pre-pressurization in the gas space 45 but rather on both the pressure gradient at the throttle point 47 and the pre-pressurization in the gas space 45, the influence of the throttle point being much stronger than that of the gas space.

When the torsional vibration damper cools down, damping medium can flow from the compensating space 41 into the collecting space 33 and thus compensate for the decrease in the volume of the damping medium. If the cooling occurs very rapidly, the check valve 57 will accelerate the return flow considerably, because it bridges the throttle point 47.

Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto. 

1. A torsional vibration damper comprising: a stator having stator vanes; a rotor having rotor vanes alternatingly arranged with the stator vanes so as to form at least two work chambers fillable with damping medium, the rotor and stator being operative to oscillate relative to one another so that the at least two work chambers alternately change respective volumes, the rotor having a compensating space in flow communication with the at least two work chambers; at least one damping device separating the compensating space into a pre-pressurized space, a first collecting space and a second collecting space, each of the first and second collecting spaces being in flow communication with the at least two work chambers; and a throttle point provided in the at least one damping device and configured to provide flow communication between at least one of the first and second collecting spaces and the pre-pressurized space.
 2. The torsional vibration damper of claim 1, further comprising a first connection radially extending between the first collecting space and one of the at least two work chambers, and a second connection radially extending between the second collecting space and the other work chamber.
 3. The torsional vibration damper of claim 1, wherein the throttle point is configured to exert a stronger throttling effect at higher flow velocities of the damping medium between the at least one collecting space and the pre-pressurized space than at lower flow velosities.
 4. The torsional vibration damper of claim 1, wherein the throttle point is configured to provide flow of the damping medium between the pre-pressurized space and the at least one collecting space in at least one of opposite directions.
 5. The torsional vibration damper of claim 1, wherein the throttle point is configured to provide flow of the damping medium between the pre-pressurized space and the at least one collecting space in opposite directions.
 6. The torsional vibration damper of claim 1, wherein the damping device includes a check valve connected in parallel to the throttle point, the check valve being operative to prevent flow of the damping medium from the at least one collecting space to the pre-pressurized space and to provide flow of the damping medium from the pre-pressurized space to the at least one collecting space.
 7. The torsional vibration damper of claim 1, wherein the throttle point includes a porous component.
 8. The torsional vibration damper of claim 7, wherein the porous component is made of sintered material.
 9. The torsional vibration damper of claim 1, wherein the damping device includes first and second partitions spaced from one another so as to define the pre-pressurized space, the first collecting space, and the second collecting space arranged coaxially with one another and extending in series along the compensation space.
 10. The torsional vibration damper of claim 9, further comprising a rod axially extending through the first and second partitions and coupled therewith so as to form a unit. 